This invention relates to a process unit adapted to be removably mounted in a main assembly of an electrostatographic reproducing machine, the unit comprising a housing and an imaging member inside the housing. The invention further relates to an electrostatographic reproducing machine employing such a process unit.
In the art of electrostatographic reproduction there is a trend to incorporate the imaging member, i.e. the photoreceptor, together with other process means such as a charge corotron, a development device, and a cleaning device in a removable process unit or so-called cassette as disclosed for example, in U.S. Pat. No. 3,985,436 to Tanaka et al. The use of such a cassette enables the easy replacement of those parts of the copying machine which are most likely to deteriorate with use, especially the photoreceptor, but also the development and cleaning systems as well as the charge corotron wire. A further advantage of containing the major process elements within a cassette is that interchangeable cassettes may be used in a given copying machine to provide different development characteristics or different coloured development.
A problem with the cassette disclosed in U.S. Pat. No. 3,985,436 is that when it is removed from the main assembly of the copying machine the part of the imaging member where image transfer occurs in the copying machine is unprotected and is therefore susceptible to damage or contamination, and also to light exposure which can result in premature deterioration of the photosensitive material on the imaging member. Needless to say, these adverse affects are likely to impair the quality of image formation.